Selenium Clinical Evidence

Nutrition and Cancer
Reid ME, et al. The nutritional prevention of cancer: 400 mcg per day selenium treatment. 2008;60(2):155-63. 

Topic: 
Does 400 mcg of selenium supplementation daily decrease total cancer incidence?

Background:
Population studies indicate that people with higher selenium status are at decreased risk of cancer. The Nutritional Prevention of Cancer (NPC) study found that 200 mcg of selenium per day decreased total cancer incidence by a statistically significant 25%. What happens when the daily selenium dosage is increased to 400 mcg daily?

Study Type:
Human clinical intervention trial

Study Design:
Placebo-controlled: Patients were assigned to take either a daily selenium supplement or placebo.

Subjects:
424 patients

Dosage:
400 mcg of selenium per day or placebo

Results:
The researchers found that 400 mcg per day of selenium had no effect on total cancer incidence.

Conclusion:
Lower dosages of selenium may be preferred for cancer prevention. 

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Clinical Cancer Research 
Sabichi AL, et al. Selenium accumulation in prostate tissue during a randomized, controlled short-term trial of l-selenomethionine: a Southwest Oncology Group Study. 2006 Apr 1;12(7 Pt 1):2178-84. 

Topic: 
Does selenium selectively accumulate in prostate tissue?

Background:
Population studies and clinical data suggest selenium could prevent prostate cancer, but it has not been shown that supplemental selenium leads to an increased concentration of selenium in prostate tissue versus other tissues. Does it?

Study Type:
Human clinical observation trial

Study Design:
Randomized, controlled: Half of the subjects were assigned to take selenium supplements, while the other half were simply observed.

Subjects:
66 men with prostate cancer

Dosage:
[? mg] selenium (as l-selenomethionine) per day

Results:
Among men taking supplements, the selenium concentration in prostate tissue increased 22% versus those in the observation group, and was higher than in adjacent tissue.

Conclusion:
These findings support the hypothesis that oral selenium supplementation may contribute to the cancer preventive effects of selenium.

 

 

Selenium Mechanism of Action

Cancer patients, including those with prostate cancer, have been found to have reduced expression of the gene that binds selenium to protein, indicating they may be prone to deficiencies of this mineral. High intake of selenium can tamp down the biochemical pathways related to prostate cancer and various enzymes involved in the progression of prostate cancer (such as Dhcr24 and Abcc4). Selenium also inhibits the binding of nuclear factor kappa B, a protein that plays a role in the development and progression of cancer.